1. Technical Field
The present invention relates to texturizing and polishing disks. More specifically, the present invention relates to an apparatus and method for texturizing disks of the type used for magnetic storage of information.
2. Discussion of the Related Art
During operation, magnetic storage disks spin at high speeds while a read/write head floats on a cushion of air near the surface of the disk. When not in use, the read/write head typically "parks" in a special zone of the disk, usually near the inside edge. The disk surface is texturized in order to prevent the head from sticking onto the surface of the disk when parked. The texture on the disk consists of many small grooves, typically on the order of 40 angstroms from peak to valley.
Texturization of magnetic storage disks is generally accomplished by rotating the disk while bringing to bear upon each side of the disk an abrasive medium supported by a compliant "load roller". The position of the roller and medium relative to the disk is made to vary toward and away from center of the disk in an oscillatory manner. Texture grooves are formed by the abrasive particles creating non-circular patterns on the disk. It is important that the pattern of the texture grooves on the disk have certain characteristics, such as a specific intensity as well as a specific angle with respect to a concentric circle on the disk.
The oscillating motion between the disk and the abrasive medium can be accomplished in a number of ways. In one method, the abrasive media is held stationary while the rotating disk is translationally oscillated across the abrasive media. The disk is clamped in a spindle assembly which rotates the disk, while the entire spindle assembly and rotation means is mounted on a sliding base. Typically a cam and follower arrangement act to oscillate the base, spindle assembly and disk. An example of a cam-based method is the Model 1800A Automated Surface Finisher made by Exclusive Design Company, the assignee of this application. In another arrangement, the center of the rotating disk is held stationary while the abrasive media, rollers and magazine assembly are translationally oscillated in horizontal directions parallel to the plane of the disk with a stepper motor and lead screw. An example of this method is the Model 1800 Automated Surface Finisher made by Exclusive Design Company.
In both of these methods of texturization, the oscillating motion requires that a substantial amount of mass be continuously accelerated and decelerated. The accelerations, which are transmitted to the frame of the apparatus cause undesirable vibration. The vibration may be severe enough to effect various element on the texturizing machine. For example, the load rollers may begin to vibrate resulting in chatter or undesired patterns on the disk.
Increasingly, disk texturizing processes are requiring higher frequency oscillations in order to increase throughput. Processes are also increasingly requiring that the position and velocity of the oscillator be more precisely controlled. Both higher oscillation frequencies and more precise positioning result in greater accelerations and therefore impart an increased amount of force on the system.
Moreover, texturizing patterns are increasingly required to be "triangular" rather and sinusoidal, meaning that the grooves on the disk consist primarily of straight lines rather than rounded sinusoidal sections. Triangular texturizing patterns result in more consistent "crossing angles" which are defined as the angles between the grooves and the path of a read/write head. In order to texturize a disk with a highly triangular texturizing pattern, higher accelerations and decelerations are generally necessary since the oscillator must reverse directions more quickly.
Thus, with increasing amounts of acceleration being exerted on the frame of the texturizing machine, problems such as load roll chatter and vibration which effect the resulting texture pattern on the disk are increasing as well. Therefore, there is an increased need to alleviate the magnitude of the overall force transmitted to the frame of the system due to the accelerations.